1. Field of the Invention
Aspects of the present invention relate to a system and method of improving a saturation of a red-green-blue-white (RGBW) image signal, and more particularly, to a saturation improvement method and system that can increase a backlight luminance and decrease a luminance of W sub-pixels and thereby prevent a deterioration in a saturation of a pure color occurring when an RGB image signal is converted into an RGBW image signal.
2. Description of the Related Art
As compared to a red-green-blue (RGB) display, a red-green-blue-white (RGBW) display generally includes a white (W) sub-pixel, thereby improving the entire saturation of the display. In addition, the RGBW display requires a smaller number of integrated circuits (ICs) to drive a display. Therefore, the RGBW display can display image signals with low costs and high luminance.
However, due to the W sub-pixel added in the RGBW display, the saturation of pure colors included in the image signal may be deteriorated. Specifically, an absolute digital value of a pure color is the same as that of the RGB display. However, when the RGBW display includes a background, the luminance of the pure color may be relatively deteriorated because the luminance of the background is greater than that of the RGB display due to the W sub-pixel. Because of the relative luminance difference, the RGBW display has a relatively deteriorated saturation of the pure color in comparison to the RGB display. The pure color may have the highest saturation for a particular color tone.
For example, it is assumed that there exists a frame of an image signal having a letter in yellow and a background in grey. The yellow may be a pure color and be represented as a digital value (255, 255, 0). When representing the image signal using the RGBW display, the luminance of the background in grey is relatively greater than in the RGB display due to the W sub-pixel. Thus, the letter in yellow may look relatively darker. However, the luminance value of the background in grey is the same for both the RGB display and the RGBW display.
Although the luminance value of the grey background is the same, the background in the RGBW display may look relatively more luminous than in the RGB display due to the W sub-pixel. Accordingly, when the RGBW display is compared to the RGB display, the RGBW display may make the yellow letter appear relatively darker, resulting in a decreased saturation, although the yellow letter included in the grey background has the same absolute digital value in both the RGB display and the RGBW display. This problem may become more serious when a pure color having a higher saturation (such as yellow) is included in the entire frame.
In comparison to the conventional RGB display, the RGBW display has an advantage in that a manufacturing cost can be reduced due to a smaller number of ICs to drive the display. Moreover, due to the W sub-pixel, an image with high luminance may be readily represented and a number of backlights may be reduced. However, as described above, since the saturation of the pure color may deteriorate due to the W sub-pixel, there is a need for a method and system for improving the saturation.